11-08-15 01:20 Computer Nerd Kev wrote to Keith Matthews about Re: C-64 with no
9v possi
Howdy! Kev and Keith,

 CNK> @MSGID: 
 CNK> Keith Matthews 
 CNK> wrote:
 > Hi All,
 >
 > I have a breadbox style C-64 that has stopped working.
 > I connected my 1501 Power Monitor to the Power Supply and it
 > seems fine for both 5v and 9v (well it shows 10v)
 >
 > The Power Supply work fine with my C64C machine.
 >
 > I connect the 1501 Power Monitor to the User Port and I
 > only get the 5v indication
 >
 > There does not seem to be 9v at the user port.
 > I have pressed in all the chips and checked the internal fuse on the C-64.

 CNK> If the power supply 9V voltages are alright when used with your C64C,
 CNK> but drop when used with this one, it could be due to a short in the
 CNK> computer causing excessive load and in turn the 9V voltage to drop
 CNK> below that required by the computer. That could be due to a failed
 CNK> capator or other component connected to the 9V supply.

 CNK> Also use a multimeter in its lowest resistance mode to check that there
 CNK> is very low resistace between the 9V pins of the power plug at the back
 CNK> of the computer, and the 9V pins of the User Port.

 CNK> There are a pair of pins to check for this:
 CNK> Power pin 7 to User Port pin 11
 CNK> Power pin 6 to user Port pin 10

 CNK> If there is more than a few ohms resistance, there could be a partial
 CNK> or complete break in the circuit board, or in the connection for the
 CNK> power plug.

 CNK> If it is a low resistance, but the 9V voltage reading is low when the
 CNK> computer is on, then a component failure or other short inside the
 CNK> computer is likely.

 CNK> If the 9V fuse in the computer hasn't blown, you might try removing it
 CNK> and connecting your multimeter in its highest current measureing range
 CNK> across the fuse terminals. With the computer breifly switched on, you
 CNK> may observe the current above or near the 1A maximum rating which would
 CNK> indicate a short or component failure. This test should be breif, as
 CNK> the excessive load does risk overheating the transformer in the power
 CNK> supply.

I was thinking if there was a small crack in a circuit board trace,
solder a wire across the gap.

I have also used small copper material made by Bishop Graphics to repair
PC Boards.
The Bishop Graphics stuff looks neater but either method will do the job.

... I got an idea. My brain cell is aching something fierce!
--- MultiMail/MS-DOS v0.49
--- SBBSecho 2.12-Linux